Refining of animal and vegetable oils



May 1, 1945.

B. CLAYTON REFINING OF ANIMAL AND VEGETABLE OILS Original Filed Sept.26, 1939 lutomm b Patented May 1, 1945 Q 2,374,924 DEFINING OF511131115? AND VEGETABLE Benjamin Olayton, Houston, Tex assignor, by

meme assignments, to Befinin g, Unincorporated, a Texas partnershipOriginal application September 26. 1939, Serial No. 296,685. Divided andthis 17, 1941, Serial No. 398,189

application June 6 Claims. (Cl. 200-426) This invention relates to aProcess of refining or partially refining animal and vegetable oils.

Caustic alkalies in amounts providing large excesses have beenconventionally employed in the complete alkali refining of animal andvegetable oils to neutralize the free fatty acids thereof and formseparable soap stock. Such excesses of caustic alkalies saponify neutraloil to produce refining losses. Also, substantial amounts of neutral oilare lost by entrainment in the soap stock when this soapv stock isseparated from the oil. The employment of caustic alkalies in excess asthe neutralizing agent has been considered necessary for completerefining in order to produce a separable soap stock and also in order toreduce the color of certain oils.

In accordance with-the present invention, it has been found thatnon-saponifying neutralizing agents may be employed for completerefining so as to substantially eliminate losses by saponification ofneutral oil and also that the proper employment of softening or dilutingagents for soap stock or other foots provides efilcient separation ofthe soap stock from the oil and reduces entrainment of neutral oil. Thepresent invention also contemplates the employment of oil solventsduring a refining operation together with a partial or completedehydration step to remove the solvent, the dehydration step beingemployed after adding the refining agent and prior to separation. Thedehydration step is preferably followed by a rehydration step prior toseparation. Certain of the steps of the present invention may beemployed in combination with the use of caustic alkalies as neutralizingreagents to reduce refining losses, even if the conventional excesses ofsuch caustic alkalies are employed. The present invention also enableslower excesses or no excess of caustic alkalies to be employed in theneutralization step so as to reduce or eliminate losses due tosaponification oi neutral oil while still providing effective separationof the soap stock and adequate color reduction. Furthermore, certainsteps of the present invention are effective to reduce refininglosses inacid refining processes or in partial refining or degumming operationsemployed to condition the oil for more effective alkali refining or forthe production of non-break oil.

The object of .the present invention is to provide a process of refiningor partially refining vegetable and animal oils in which refining lossesare markedly reduced.

In describing the present invention, reference will be had to theaccompanying drawing of which:

Figure l is a schematic diagram of apparatus in which certain steps ofthe process of the present invention'may be performed; and

Figure 2 is a similar diagram of a modified apparatus.

Referring more particularly to Figure 1: i0 indicates a tank for oil tobe refined, ll indicates a tank which may contain either a refiningagent or adiluting or softening agent for the soap stock or other foots,and I2 indicates a tank for an additional refining or other agent. Theoil may a be brought to a predetermined temperature by a heating coil l3positioned in the tank I0, and may be withdrawn from the tank by a pump[4 and passed through a heat exchange device I5. to a flow mixer l6. Theheat exchange device may include a coil l1 through which the oil ispassed, which coil is positioned in a casing i8 through which anydesired heating medium may be circulated. Neutralizing or other refiningagent may be heated in the tank ll, withdrawn by a pump 20 and deliveredto the fiow mixer IS. The fiow mixer l6 may be of any desired type ofclosed mixing device such as'a closed mechanical agitator or colloidmill. In many cases the mixer may merely be a means for injecting aflowing stream of the agent into a fiowingstream of the oil.

The mixture or oil and agent may be passed through a second heatexchange device 2|, and then delivered to a second fiow mixer 22.Additional agent may be brought to a desired mixing temperature in thetank I2, withdrawn by a pump 24 and delivered to the fiow mixer 22. Foralkali refining, at least one of the agents added in the mixers It or 22contains sufiicient neutralizing agent to neutralize the free fattyacids and form soap stock. The pumps I4, 20 and 24 are preferablyarranged to deliver accurately proportioned streams of the variousmaterials. One way of accomplishing this is to drive the pumps by avariable speed electric motor 25 with variable speed devices 26 and 21positioned between the motor and the pumps 20 and 24. The resultingmixture may be passed through another heat exchange device 28, Asdiscussed below, the continuous mixing steps just described can beemployed to deliver a mixture to a vapor separating chamber describedbelow with reference to Figure 2 and, if continuous centrifugalseparation is to be employed, the mixture from the vapor separatingchamber can be rehydrated and delivered to a continuous centrifugalsepainto a receiver 3|.

centrifugal separator as a liquid heavy ei'liuent as the light eiliuentinto a receiver I3. If the neutralized oil is too highly colored, it maybe withdrawn from the receiver 33 by a pump 34 and passed through a heatexchange device 35 to a flow mixer 36. A color reducing agent heated toa desired temperature may be withdrawn from a tank I! by a pump 38 anddelivered to the flow mixer 36. Pumps 34 and 38 may also be arranged todeliver accurately proportioned streams by driving the pumps with avariable speed electric motor 40 and providing a variable speed deviceII between the motor 40 and the pump 38. The mixture of oil and colorreducing agent may then be passed through one or more heat exchangedevices 42 and I1 and delivered to a continuous centrifugal separator 44in which the color impurities are separated from the oil Neutralized oilis discharged agent under certain conditions, as described hereinafter.Soda ash is, however, a preferred nonsaponifying neutralizing agent. a

While continuous flow mixing of the oil and agents under pressure andout, of contact with the air is preferred, it is possible to mix a bodyof oil with a soda ash solution in a mixing receptacle such as shown inFigure 2, as the soda 7 ash will not saponify neutral oil even uponproand discharged as the heavy efliuent into -a receiver 48. The oil isdischarged as the light emuent into a receiver 40. The color reductionstep may be omitted if the color of the neutralized oil in the receiverll is sufficiently low and is not ordinarily employed with acid refiningor partial refinin Following alkali or acid refining, the oil dischargedinto the receiver 40, or, if the color reduction step is omitted, theoil discharged into the receiver 33, is desirably washed and vacuumdried by withdrawing a stream .of the oil by a pump 49, passing the samethrough a heat exchanger ill to bring the oil to a desired mixingtemperature, which is usually between 120 and 200 F., and delivering thestream into a flow mixer ii. A stream of water heated to the desiredmixing temperature may be withdrawn from a tank 52 by a pump 53 anddelivered to the mixer ii, in amounts ranging between and 30% of the oiland usually about The resulting mixture may then be passed through acentrifugal separator 55. The temperature for most effective separationordinarily ranges belonged contact. Thus, oil can be introduced into areceptacle 6-9 through a pipe 10 and soda ash solution introducedthrough the pipe 1|. The receptaclemay be provided with an agitator 12driven from any suitable source of power so that a thorough admixture ofthe oil and neutralizingv agent can be produced. The receptacle may alsobe provided with a heating coil II for heating the mixture during orsubsequent to mixing. The

I 'mixture of oil and resulting soap stock may be withdrawn from thereceptacle by a pump 15 and passed through a heat exchange device 16.The mixture may then be introduced'into a vacuum chamber 11 providedwith a heating'coil 18 and an agitator 19. with some oils it has beenfound preferable to substantially completely dehydrate the mixture inthe vacuum chamber by withdrawing water vapors into a condenser 82 in Iwhich the water is condensed and delivered as liquid water to a receiver83. However, with other oils it has been found sufflcient to merelyremove gaseous-materials such as air and carbon dioxide while removingonly a portion of the water. .The employment of very dilute solutionsheat exchanger 54 and delivered to a continuous tween 140 and 200 F. Thewater containing dissolved impurities is discharged as the heaviereiluent into a receiver 6 and the washed oil is discharged as the lightefliuent into a receiver 51.

The washed oil may then be withdrawn from the receiver 51 by a pump 50,passed through a heat exchanger I! and delivered into a vacuum chamberat a temperature which is preferably between 160 and 210 F. The vacuumchamber is preferably provided with an agitator ti and with a heatingcoil 63. It may also be provided with a steam distributor 0| so thatsteam, preferably superheated, may beintroduced to agitate the oil andassist in carrying oflf water and other vapors. Vapors may be withdrawnfrom the vacuum chamber into a condenser provided with a receiver 66, bya vacuum pump 61. A relatively high vacuum, for example between 2'! and29 inches of mercury, is. preferably maintained in the vacuum chamber.Temperatures in the vacuum chamber will usually range between 160 and.

200 F. for drying the oil, although the temperature may be increased upto 350 F. and the oil treated with superheated steam in order todeodorize the oil. The washed and dried oil may be removed from thevacuum chamber and discharged from the process by a pump Bl.

NOII-SBIDODHYHIK neutralizing agents, that is. agents which will notsaponify neutral oil but which will react with free fatty acids presentin of soda ash in conjunction with dehydration is particularly effectivewith some oils, as the dilute solution modifies the gums'to produce moreeilec- I tive separation and the dehydrator may be 'employed to bringthe water content of the mixture to that producing most effectiveseparation. The solution initially added may even be sufliciently dilutethat neutralization does not take place until after partial dehydration.A vacuum pump 84 may 'be connected to the receiver to maintain a vacuumin the vacuum chamber. The

vacuum chamber may also beprovided with a steam distributor 85 throughwhich steam, preferably superheated, may be introduced into the oil toassist in carrying of! the'vapors and agitating the oil.

A dehydrated or partially dehydrated mixture of oil and soap stock maybe withdrawn from the vacuum chamber by a pump 06 andpassed through aheat exchanger 81 into a mixer 88. If the mixture of oil and soap stockwithdrawn y from the vacuum chamber contains less water or soap stocksoftening agent than that providing effective separation, it may berendered separable by admixing therewith a stream of rehydrating rdiluting a ent withdrawn from a tank 09 by a pump and delivered to themixer 00. The preferred rehydrating agent is an aqueous solution of sodaash. although other agents may be employed as hereinafter described. Therehydrated mixture may then be passed through another heat exchangedevice 9|. If desired, additional rehydrating agent of the same ordifferent kind or concentration may be withdrawn from a tank 92 by apump 93 and delivered into a mixer 94,

into which the mixture from the heat exchange device 0| may also bedelivered. The resulting mixture may then be passed through another heatexchange device 9! and delivered to a continuous centrifugal separator98. With certain oils sufiicient rehydrating agent of the correctconcentration may be introduced into the mixer 88 so that the mixer 84and heat exchange device 95 may be eliminated. If sufllcient soda ash orother agent was admixed with the oil prior to dehydration, therehydrating agent may be water alone. In any case, the amount andconcentration of soda ash or other solution present during separation inthe separator 96 will be similar to the amount specified with referenceto the process of Figure 1, although the dehydration treatment willusually enable a lesser amount to be employed. Thin liquid soap stock isseparated from the refined oil and discharged as the heavy effluent intoa receiver 98 and neutralized oil is discharged as the light effluentinto a receiver Hill. If necessary. for further color reduction. the oilmay be withdrawn from the receiver I and subjected to a color reductionstep similar to that described with reference to Figure 1. after whichit may be washed and dried or. if the color of the oil is sufficientlylow, it may be immediatel subjected to a washing and drying step.

In carrying out the proces of Figure 2, the oil in the mixing receptacle69 is usually maintained at a relatively low temperature, for example.temperatures between 70 and 100 F., as heating the oil prior to admixingwith neutralizing agent to a temperature much above 100 F. may damagethe oil. Suillcient soda Mb or other non-saponifying neutralizing agentis preferably introduced into the receptacle to neutralize the freefatty acids. When employing soda ash, it will in some cases be necessaryto add at least twice as much soda ash as that necessary to neutralizethe free fatty acids in order to prevent violent foaming in thereceptacle. This is particularly true if the mixture is heated in thereceptacle. By employing a large excess of soda ash, or very dilutesolutions thereof. the mixture may be heated to relatively hightemperatures, for example 120 to 140 F.. in the receptacle withoutexcessive foaming. The materials in the tank 69 are preferably agitatedat a relatively high speed until a thorough admixture is obtained. Theagitation may then be slowed and a stream of the mixture withdrawn fromthe receptacle by the pump 15. It is usually desirable to employ theheat exchanger I6 to increase the temperature of the mixture tobetween160 and 210 F. Upon discharging the heated mixture into the vaporseparating chamber .11, water and other vaporizable impurities arewithdrawn therefrom to form a partially or substantially completelydehydrated mixture. If a substantially completely dehydrated mixture isfound desirable for a given oil. the. employment of concentratedsolutions or slurries in the mixer 69 reduces the amount of waterremoved in the vapor separating chamber. Even dry soda ash or othernon-saponifying agent may sometimes be-employed. Any carbon dioxideformed as a result of admixing soda ash with the oil is withdrawn fromthe mixture even if dry soda ash is employed andif neutralization of theoil has not been completed in the receptacle 69. substantially completeneutralization is effected in the vapor separating chamber 11.

The treatment of the mixture of oil and soap stock in the chamber 11appears to modify the nature of the soap stock so that better separationmay be accomplished in the separator 98,

and this is particularly true if the treatment therei is sufficientlydrastic that at least a substantial portion ofthe water is withdrawn andthe mixture then dehydrated. Also, other porizable impurities arewithdrawn from the In the process above described employingnonsaponifylng alkalies, substantially no neutral oil is lost by.saponification thereof. The nonsaponifying neutralizing agents do notattack the oil and, even though caustic alkalies are employed in thecolor reducing step, the small amount and the short time of contact withthe oil, as well as the efficient separation obtainable in the absenceof soap stock, enables color reduction to be carried on with nosubstantial saponiflcation of neutral oil. The losses during the colorreduction step are usually not greater than of 1%. The losses in theneutralizing step are due substantially entirely to entrainment ofneutral oil in the soap stock and are usually less than half thoseordinarily encountered in the best prior processes. All of the steps ofthe process may be rapidly performed so that the:oil is not subjected tohigh temperatures for extended periods of time.

It is apparent that the continuous step of mixing oil and neutralizingagent shown in Figure 1 may be employed with thedehydration step ofFigure 2 as stated above.

The dehydration step including vapor and gas separation shown in Figure2 is particularly adaptable to refining oils containing oil" solvents.as such solvents are removed from the oil in the vacuum chamber 11.Thus. such solvents as hexane, benzene, gasoline, benzol and otherpetroleum solvents employed to extract the oil from the seeds may bepresent in the oil so that it is unnecessary to remove the same prior torefining; The presence of such solvents is often desirable, as thesolvent vapors separated from the oil assist in removing vaporizableimpurities from the oil and if caustic alkalies .are employed forneutralization such solvents inhibit saponiflcation of neutral oilthereby. It is, therefore, sometimes desirable to add such solvents evenif not originally present in the oil. Also. other vaporizable materialssuch as ethyl or isopropyl alcohol, or other fatty acid or soapsolvents. may be added to the oil either alone or in combination withthe petroleum solvents above referred to. Such solvents also inhibitsaponification of neutral oil by caustic alkalies. The various. solventsappear to modify the nature of the gums and soap stock so that moreefiectisve se aration is accomplished in the separator 9 ber may berecovered by condensing the vapor thereof and may be again used in theprocess.

Instead of employing a separate color reduction step such as thatdisclosed in Figure 1 when non-saponifying neutralizing agents areemployed. it'is sometimes possible to secure suflicent color reductionof the oil b adding a small amount of caustic alkali solution to the oiland soap stock mixture prior to the separation of the soap stock fromthe oil. Thus the mixer 22 of Figure l and the mixer 94 of Figure 2 maybe employed for this purpose. A small amount of caustic alkali' solutionmay thus be added alone or in admixture with soda ash or other dilutingthe treatment in the The solvents removed in the vacuum chamlargeamounts of free solution. Thus with certain oils, even when employingncn-saponifying agents for neutralize-- tion, the subsequent colorreduction step may be eliminated, without substantial increase ofrefining losses even though rather highly colored, by adding causticalkali after neutralization but before separation of the soap stock.

It is also possible to admix a small amount of caustic alkali such ascaustic soda with the sodaash solution initially admixed-with the oil sothat less soda ash solution-is necessary to neutralize the free fattyacids while preventing the formation of carbon dioxide. This operationis particularly useful when refining oils. containing fatty acids. Ifthe amount of caustic alkali thus added is not greater than thatnecessary to neutralize in the oil, no saponification of neutral oiltakes place during the neutralizing step. Just suflicient caustic alkalisolution to neutralize the free fatty acids may also be employed as theneutralizing agent in the absence of soda ash, even when the mixture isdehydrated, without materially increasing refining losses if sufllcientsoda ash or equivalent soap stock softening solution is added prior toseparation to soften the soap stock and provide effective separation.

The process of the present invention has been particularly describedwith reference to the employment of soda ash solutions, since suchsolutions, if employed in sufllcient amount and of proper concentration,effectively soften the soap stock and produce an extremely liquid soapstock. Also, such soda ash solutions eifectively drive the oil out ofthe soap stock phase so that very little oil is retained in the soapstock. However, other non-saponifying neutralizing agents such astrisodium phosphate, disodium phosphate, sodium silicate, equivalentpotassium salts and other alkaline salts of alkali earth metals are alsoeffective. Also, amines such as ammonia, triethanolamine, etc., may beemployed as neutralizing agents in any process not involvingdehydration, as they not saponify neutral oil. It is not necessary thatalso produce softened soap stock and do all of the agent present duringseparation be basic in nature, as certain substantially neutral saltssuch as sodium sulfate, sodium thiosulfate, sodium thiocyanate, etc.,and equivalent potassium, ammonium and alkali earth metal salts whichalso soften the soap stock may be substituted in part for the ing agent,so long as sumcient neutralizing agent is present to substantiallycompletely neutralize the free fatty acids. The equivalent potassiumsalts are usually even more effective than sodium salts but arerelatively expensive. Even a small amount of acidic materials such asnaphthenic acid which react with alkalies to form very liquid soaps maybe employed. Abietic acids, such as those found in rosin, may also beemployed for the same purpose. The resulting solutions of salts of theseacids function as soap stock softening agents and reduce the-amount ofother solutions such as soda ash ecessary for effective separation. Theacids may also be converted into soap prior to introduction into theproc the 011 being refined is the free fatty acids soda ash or otherneutralizthese acids, particularly the rosin soap,

or other non-saponifying alkalies. The salts of have the advantage ofincreasing the value of the soap stock over soap stocks containinglarge. amounts of salts other than soap. Sufllcient neutralizing agentshould be employed to neutralize the free fatty acids or any otheracidic material present.

Potassium soaps are usually more liquid than sodium soaps, and it ismany times advantageous to have such soaps present during separation.This can be accomplished by substituting potassium carbonate for a partor all of the sodium carbonate as the neutralizing agent. Potassiumlwdroxide can also be substituted for caustic soda wherever caustic sodais disclosed herein.

Also, a potassium soap solution may be added as a rehydrating or soapstock softening solution. Certain other bases such as urea also pro-.

duce very liquid soaps and can be employed as neutralizing agents eitheralone or in combination with other agents to soften the soap stock,

or soaps of urea or similar bases may be added either before or afterneutralization as a soap stock softening agent. In many cases, however,the soap stock softening agent may consist in whole or in part ofsubstantially neutral salts which have a softening effect upon the soapstock. Various mixtures of such salts, other stock softening agents andneutralizing agents maybe present during centrifugal separation so longas the amount and concentration of the solution is sufllcient to producea liquid soap stock containing very little neutral oil. The amount andconcentration of such solutions will vary with different oils and agentsemployed but will usually fall within the range of concentrations andamounts given with respect to soda ash solutions. The employment of suchsoap stock softening agents in" relatively large amounts is particularlyimportant when refining oils such as palm oils, which form soaps whichare hard and relatively insoluble. With some oils it is sometimespossible to employ relatively large amounts of water alone as' thediluting agent. Certain salts, for example, chlorides such as sodiumchloride, are not effective to produce the improved separation of thepresent invention, as they harden instead of soften the soap stock.

' While continuous centrifuga1 separation produces much better resultsthan settling operations, improved results over prior batch processesare obtained by employing large amounts of solutions of thenon-saponifying neutralizing agents,'salt solutions, or other soap stocksoftening agents, above discussed during a batch settling operation. Thesoap stock layer is more compact and contains less neutral oil and thereis a sharp line of usually effective for batch settling operations.

Thus continuous mixing of the neutralizing agent may be combinedwith abatch settling 0peration, a batch mixing operation may be comess. Theacids or soaps may be added prior or I v the absence ofsubstantlal-excesses of soda ash bined with a continuous centrifugalseparation,

or both separation and mixing may be continuous or batch. Colorreduction and separation of color impurities as well as washing anddrying may also be continuous or bat'chr In fact, an entire refiningoperation, including mixing, dehydrating, rehydrating or diluting, soapstock separating, color reduction and washing and drying, or anyselected number of these steps may is employed. The oil resulting fromcan, however, continue 2,874,994 be carried out in a single kettle ifdesired. The

soap stock softening vention agents of the present inor settling step,

a layer containing a mixture of oil and soap, and

tion. The dehydration treatment also aids in preventing thisstratiflcation.

In any case, the employment oi large amounts of non-saponifyingneutralizing agents during separation, or the employment of diluting orsoap stock softening agents mentioned herein, results in a more completeseparation of the oil from the soap stock. When non-saponifyingneutralizing agents are employed, there is substantially no loss arisingfrom saponification of neutral oil. Color reduction steps performed onthe oil from which the soap stock has been removed also producenegligible refining losses. amount of solutions present during soapstock separating and the washing step remove substantial amounts ofcolor impurities even if no caustic alkalies or separate color reductionstep the process is of high quality and, if desired, of low color. Oneof the major advantages of the ess is its adaptability to substantiallyall types of vegetable and animal oils. Thus, vegetable oils such ascottonseed, corn, sesame, soya bean, linseed, etc., can be treated. Eventung oil, which is extremely difiicult to refine because of emulpresentprocsion difliculties, may be satisfactorily refined, particularly in aprocess involving dehydration, as such dehydration completely breaksemulsions formed during neutralization. The vegetable oils may be eithercrude oils containing gums, or may be so-called degummed oils from whichthe ummy materials have been previously removed. The term "animal oils"is intended to include fish oils, suchas sardine, menhaden, herring,etc.

The employment of the dehydrating step of the present invention, evenwhen caustic alkalies, such as caustic soda, withthe conventional largeexcesses are used as the neutralizing agent, produces improved results.Continuous mixing as disclosed in Figure 1, either with stream preheat-ving to temperatures between .100 to 160 F. or subsequent stream heating,is preferable as the mixture can be delivered into the dehydratingchamber of Figure 2 before substantial saponification of neutral oiltakes place. Also, rapid and substantially complete dehydration is alsopreferred as removal of substantially all of the water prevents orsubstantially retards further saponification of neutral oil.

to act as a color adsorbing agent in the presence of excess caustic. Byrehydrating the mixture and promptly centrifugally a more efiectiveseparation can be saponification of neutral oilduring saponiflcation, v

The dehydrated soap stock and are removed in use in the process, ifdesired.

When employing the usual excess of caustic neutralizing agents, wateralone may be used as tion independent of the separation step. Thus, verydilute solutions can be employed for neutralization for certain oils andseparation carried out in the presence of more concentrated solutions.

The dehydration and rehydration steps or the employment of softeningagents for the acid ioots also reduce refining losses in acid refiningprocesses. Such acid refining processes involve the mixing of solutionsof strong mineral acids, such as sulfuric or phosphoric, with the animalor vegetable oils in order to render separable impurities other thanfree fatty acids. Acid refined in the paint and varnish industries foruses where the presence of free fatty acids is desirable or at leastunobjectionable. Such acid refining processes are preferably carried outby employing the continuous mixing steps described 1. Relativelyconcentrated solutions are usually employed and the acid will not onlycause splitting ofthe glycerides in the presence of water but willalso-attack the oil to cause sulfonation, etc.,

depending upon the acid employed. By rapidlyv dehydrating the mixtureafter the acid refining therewith, these reactions erties of the refinedoil.

the dehydrating step for rewith reference to Figure impurities generallyreferred soaps of naphthenic or rosin vto a second continuous agentsshould be used to combine with the alkali and still leave sumcient acidto render the acid foots separable. The reaction products of the acidand alkali then constitute the softening agents. If carbonates areemployed in this manner, it is usually necessary to use a dehydrationstep and add the carbonates before dehydration in order to remove carbondioxide and prevent it from interfering with separation. Neutral saltsand acidic softening agents above disclosed can be employed withoutnecessitating an increase in the amount of acid refining agent. Y

The dehydrating step and facts softening agents are also applicable'topartial refining or degumming processes employing weak acids or bases orsubstantially neutral so utions or even water to precipitate foots.Water alone, weak solutions of strong acids or strongalkalies, and moreconcentlated solutions of weak acids or bases or of substantiallyneutral salts will render separable to as gums. A dehydration step, eventhough water alone is employed to precipitate the gums prior todehydration, renders the gums more easily separable when againprecipitated even though removal of water during dehydration may causesome of the gums to'again disperse in the oil. Again, adding watereither alone or carrying a softening agent provides an improvedseparation over that when the dehydration step is omitted. The presenceof softening agents during separation further improves the separation soas to reduce the oil entrained in the foots. This is true even if thedehydrating step is omitted. It is apparent that the softening agentsemployed in' degummin processes should be neither strong alkali norstrong acid. However, substantially neutral salts of alkali metals,including the potassium soaps of fatty or other acids, the sodium orpotassium acids, formamide, urea, sodium and ammonium sulphamates, areparticularly suitable and solutions thereof are preferably added afterthe gums have been precipitated and prior to separation.

In connection with the alkali refining of animal and vegetable oils, thedehydration step described makes it possible to employ other methods ofseparation than those depending upon difference of specific gravity. Forexample, the soap stock can be filtered out of the oil. This ispreferably accomplished by acontinuous vacuum filter in which the soapdeposited upon the filter member is continuously scraped therefrom.

When substantially all of the water has been rapidly withdrawn while thesoap stock is suspended in the oil,'as is the case in hydration stepdisclosed, the ing upon the filter member soap stock collecthas agranular or open structure and the oil is more easily with- The soapstock after filtration still contains some oil which can be recovered bymixing an oil solvent such as benzene with the dehydrated and filteredsoap stock and again filtering. Alternatively, the soapv stock can bewashed with solvent while'on the filter member. It is preferred,however, to continuously scrape the filtered soap stock from the filtermemher and deliver it to a mixing device concurrently with a stream ofsolvent, withdrawing a stream of the mixture from the mixer anddelivering it filter in which the mixture is continuously separated andsubstantially oil free soap stock. The oil can then be freed of solventby volatilization, for example, by heating a stream of oil-solventmixture and delivering the heated mixture into the continuous demanneras the filtration. Also, a continuous into a solventoil phase,

a vapor separating chamber such as that shown in Figure 2. The vaporizedsolvent can then be condensed and reused. A more desirable operation isto reutm the for example, by proportioning a stream of the same into astream of the oil prior to mixing the refining reagent therewith or,less desirably, just aftermixing the refining reagent with the oil. \Thesolvent is then present during neutralizatlonl or immediately thereafterand to inhibit any saponification of neutral oil, the solvent is removedin the dehydration step and may easily be condensed and separated fromthe water for reuse in removing oil from the filtered soap stock. Asimilar series of steps can also be employed with respect to dehydratedacid foots filtered from the oil in a manner similar to that A basketcan be treated to centrifugal separater can be used to separate thefoots from the dehydrated mixture by introducing a stream of water or asolution containing softening agents int .the bowl of the separatoradjacent the periphery thereof so as to cause the foots to becontinuously discharged as a stream without the diluting or softeningliquid coming into contact with the oil. Any soap ,leftin the oil can beremoved in a subsequent color reduction or washing step.

As stated above, non-saponifying alkalie particularly soda ash, are thepreferred neutralizing and soap stock softening agents for alkalirefining. Soda ash not only valuable detergent. The soda ash is lessdestructive to the gums contained in the oil and soap stock than causticalkalies, so that a better quality soap stock is produced even whenrefining undegummed oil. The decomposition products of materials such asproteins and phosphatides are amine-like, evil smelling compounds andare largely avoided when soda ash or other non-saponifying employed forrefining, particularly a a quick continuous process. separated insubstantially undecomposed form from soap stock and recovered asvaluable byproducts by washing or solvent treatment of the soap stock,although for some detergent purposes I quality filled soap is directlyproduced. By controlling the amount of water employed in the rehydratingor soap stock softening agents, a neat soap, 1. e. one containingapproximately 30% water, can be directly produced so as to be capable ofbeing converted into any type of soap product by known commercialmethods. Other types of non-saponifying alkali refining agents or soapstock softening agents which will funuction as soap fillers may besubstituted in part or wholly for the soda ash in the refining processto produce the detergents discussed above.

This application is a division of copending application Serial No.296,685 filed September 26, 1939, now issued as Patent No. 2,249,701.

While I have described the preferred embodi oil-solvent mixture to the Ieffects a low loss refining operation but the resulting soap stock is a2,374,924 ments of my invention, it is understood that the detailsthereof may be varied within the scope of the followin claims.

I claim:

1. The process of refining table oils which comprises neutralizing freefatty said filter with from.

4. The process of refining animal and vegebl ta e oils which comprisesmixing a proportioned stream oi said oil and portioned stream of anaqueous alkaline refining and thereafter continuously centrifugallyseparating said soap stock from said oil.

and soap stock, vaporizing volatile substances including substantiallyall of'said solvent from said mixture, and separating said soap stockfrom said oil.

6. The process of refining animal and vegetable oils BENJAMIN CLAYTON.

CERTIFICATE OF CORRECTION.

Patent ms. 2, 7h,92l

BENJAMIN CLAYTON.

ond column, line I for column, line 14,, for "reutrn" read--function--,- drated" 6, after "oil" insert --solvent--,- be read withthis correction ther-ei 0rd oi the case Signed read (Seal) dehydra ted nin the Patent Office.

and sealed this 7th day of August, A. o. 1915.

read --rehydrated--; --return--; line 68, second column, insert-resulting mixture of said oil and said--; line 21;, claim and that thesaid letters Patent should that the sane may conform to Page 5, secpage6, second for "funuetion" line 8, claim 14., after "dehythe rec- LeslieFrazer 2,374,924 ments of my invention, it is understood that thedetails thereof may be varied within the scope of the followin claims.

I claim:

1. The process of refining table oils which comprises neutralizing freefatty said filter with from.

4. The process of refining animal and vegebl ta e oils which comprisesmixing a proportioned stream oi said oil and portioned stream of anaqueous alkaline refining and thereafter continuously centrifugallyseparating said soap stock from said oil.

and soap stock, vaporizing volatile substances including substantiallyall of'said solvent from said mixture, and separating said soap stockfrom said oil.

6. The process of refining animal and vegetable oils BENJAMIN CLAYTON.

CERTIFICATE OF CORRECTION.

Patent ms. 2, 7h,92l

BENJAMIN CLAYTON.

ond column, line I for column, line 14,, for "reutrn" read--function--,- drated" 6, after "oil" insert --solvent--,- be read withthis correction ther-ei 0rd oi the case Signed read (Seal) dehydra ted nin the Patent Office.

and sealed this 7th day of August, A. o. 1915.

read --rehydrated--; --return--; line 68, second column, insert-resulting mixture of said oil and said--; line 21;, claim and that thesaid letters Patent should that the sane may conform to Page 5, secpage6, second for "funuetion" line 8, claim 14., after "dehythe rec- LeslieFrazer

